------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: CPU: 2 PID: 0 at lib/refcount.c:28 refcount_warn_saturate+0x14a/0x210 lib/refcount.c:28 Modules linked in: CPU: 2 UID: 0 PID: 0 Comm: swapper/2 Not tainted 6.12.0-rc1-syzkaller-00046-g7ec462100ef9 #0 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 RIP: 0010:refcount_warn_saturate+0x14a/0x210 lib/refcount.c:28 Code: ff 89 de e8 78 1c fe fc 84 db 0f 85 66 ff ff ff e8 8b 1a fe fc c6 05 e0 7e b8 0b 01 90 48 c7 c7 40 4a d1 8b e8 17 03 bf fc 90 <0f> 0b 90 90 e9 43 ff ff ff e8 68 1a fe fc 0f b6 1d bb 7e b8 0b 31 RSP: 0018:ffffc90000858930 EFLAGS: 00010282 RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff814e7329 RDX: ffff88801de88000 RSI: ffffffff814e7336 RDI: 0000000000000001 RBP: ffff88802ff899e4 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000002 R13: 0000000000000000 R14: ffff88802ff899e4 R15: 0000000000000001 FS: 0000000000000000(0000) GS:ffff88806a800000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f1510c532d0 CR3: 000000000df7c000 CR4: 0000000000352ef0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <IRQ> __refcount_sub_and_test include/linux/refcount.h:275 [inline] __refcount_dec_and_test include/linux/refcount.h:307 [inline] refcount_dec_and_test include/linux/refcount.h:325 [inline] skb_unref include/linux/skbuff.h:1232 [inline] __sk_skb_reason_drop net/core/skbuff.c:1213 [inline] sk_skb_reason_drop+0x183/0x1a0 net/core/skbuff.c:1241 kfree_skb_reason include/linux/skbuff.h:1262 [inline] kfree_skb include/linux/skbuff.h:1271 [inline] j1939_session_destroy+0x163/0x460 net/can/j1939/transport.c:282 __j1939_session_release net/can/j1939/transport.c:294 [inline] kref_put include/linux/kref.h:65 [inline] j1939_session_put net/can/j1939/transport.c:299 [inline] j1939_xtp_rx_eoma+0x327/0x660 net/can/j1939/transport.c:1411 j1939_tp_cmd_recv net/can/j1939/transport.c:2113 [inline] j1939_tp_recv+0xcb8/0xf50 net/can/j1939/transport.c:2161 j1939_can_recv+0x78f/0xa50 net/can/j1939/main.c:108 deliver net/can/af_can.c:572 [inline] can_rcv_filter+0x2a8/0x900 net/can/af_can.c:606 can_receive+0x320/0x5c0 net/can/af_can.c:663 can_rcv+0x1e2/0x280 net/can/af_can.c:687 __netif_receive_skb_one_core+0x1b1/0x1e0 net/core/dev.c:5662 __netif_receive_skb+0x1d/0x160 net/core/dev.c:5775 process_backlog+0x443/0x15f0 net/core/dev.c:6107 __napi_poll.constprop.0+0xb7/0x550 net/core/dev.c:6771 napi_poll net/core/dev.c:6840 [inline] net_rx_action+0xa92/0x1010 net/core/dev.c:6962 handle_softirqs+0x213/0x8f0 kernel/softirq.c:554 __do_softirq kernel/softirq.c:588 [inline] invoke_softirq kernel/softirq.c:428 [inline] __irq_exit_rcu kernel/softirq.c:637 [inline] irq_exit_rcu+0xbb/0x120 kernel/softirq.c:649 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1037 [inline] sysvec_apic_timer_interrupt+0xa4/0xc0 arch/x86/kernel/apic/apic.c:1037 </IRQ> <TASK> asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702 RIP: 0010:native_irq_disable arch/x86/include/asm/irqflags.h:37 [inline] RIP: 0010:arch_local_irq_disable arch/x86/include/asm/irqflags.h:92 [inline] RIP: 0010:default_idle+0xf/0x20 arch/x86/kernel/process.c:743 Code: 4c 01 c7 4c 29 c2 e9 72 ff ff ff 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa eb 07 0f 00 2d 63 ca 44 00 fb f4 <fa> c3 cc cc cc cc 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 RSP: 0018:ffffc90000197e08 EFLAGS: 00000202 RAX: 0000000000035f89 RBX: 0000000000000002 RCX: ffffffff8b21bdd9 RDX: 0000000000000000 RSI: ffffffff8b6cd040 RDI: ffffffff8bd19d40 RBP: ffffed1003bd1000 R08: 0000000000000001 R09: ffffed100d507025 R10: ffff88806a83812b R11: 0000000000000000 R12: 0000000000000002 R13: ffff88801de88000 R14: ffffffff905f2ac8 R15: 0000000000000000 default_idle_call+0x6d/0xb0 kernel/sched/idle.c:117 cpuidle_idle_call kernel/sched/idle.c:185 [inline] do_idle+0x32c/0x3f0 kernel/sched/idle.c:326 cpu_startup_entry+0x4f/0x60 kernel/sched/idle.c:424 start_secondary+0x222/0x2b0 arch/x86/kernel/smpboot.c:314 common_startup_64+0x13e/0x148 </TASK> ---------------- Code disassembly (best guess): 0: 4c 01 c7 add %r8,%rdi 3: 4c 29 c2 sub %r8,%rdx 6: e9 72 ff ff ff jmp 0xffffff7d b: 90 nop c: 90 nop d: 90 nop e: 90 nop f: 90 nop 10: 90 nop 11: 90 nop 12: 90 nop 13: 90 nop 14: 90 nop 15: 90 nop 16: 90 nop 17: 90 nop 18: 90 nop 19: 90 nop 1a: 90 nop 1b: f3 0f 1e fa endbr64 1f: eb 07 jmp 0x28 21: 0f 00 2d 63 ca 44 00 verw 0x44ca63(%rip) # 0x44ca8b 28: fb sti 29: f4 hlt * 2a: fa cli <-- trapping instruction 2b: c3 ret 2c: cc int3 2d: cc int3 2e: cc int3 2f: cc int3 30: 66 66 2e 0f 1f 84 00 data16 cs nopw 0x0(%rax,%rax,1) 37: 00 00 00 00 3b: 90 nop 3c: 90 nop 3d: 90 nop 3e: 90 nop 3f: 90 nop